Numerous processes are in use and have been proposed for the conversion of organic compounds and feedstocks to more valuable organic compounds and more valuable feedstocks for use in the organic chemical and petrochemical industries, particularly organic compounds and feedstocks derived from petroleum sources.
One promising approach to such conversion has been the oxidative conversion of organic compounds to other organic compounds. However, in many cases, such oxidative conversion processes are not commercially viable, primarily because they are energy intensive, conversions of the feedstock are low, selectivity to the desired compounds is low and such processes cannot be utilized in a continuous manner. In most of such processes the feedstocks are contacted with a solid contact material. However, there is a difference of opinion among workers in the art concerning the nature of such processes, and, particularly, the function of the contact material and the manner in which such function is performed. For example, workers in the art have at one time or another suggested that the function of the contact material involves a purely physical phenomenon, an adsorption-description process, either of atomic or molecular oxygen, either on the surface or occluded within the solid material, oxidation-reduction, utilizing multivalent metals capable of oxidation-reduction, adsorption and desorption of the organic materials on the solid materials, a free radical mechanism, etc. Consequently, the solid materials utilized are referred to variously as "contact materials", "promoters", "activators" and catalysts". Accordingly, in order to avoid functional categorization, the terms "solid contact material" or "solid contact materials" will be utilized in the present invention.
Since many processes of the prior art are based on the theory that the contact materials function via adsorption-desorption of oxygen, oxidation-reduction, etc., such processes are operated in a cyclic manner by passing an oxidizing gas over the contact material, then contacting the feedstock with the oxygen-containing contact material, and, thereafter, reactivating or regenerating the contact material by again passing a free oxygen-containing gas thereover. Such processes thus require undesirably high temperatures, are energy intensive, since the exothermic and endothermic reactions occur separately, equipment costs are high, because of the necessity for rapid cycling, and the contact material's useful life is comparatively short.
From the above, it is quite clear that the suitability of contact materials for the oxidative conversion of organic compounds is unpredictable. It is, therefore, highly desirable that new and improved contact materials for such use be developed, and that improved processes utilizing such contact materials be provided, particularly processes which lower the temperatures necessary, lower the energy requirements, are capable of being carried out in a continuous manner, extend the useful life of the contact material, improve the conversion of the feedstock and improve the selectivity to the desired products.
Of the various feedstocks for the organic chemical and petrochemical industries, olefins, such as ethylene and proplyene are of particular interest and have become major feedstocks. Of these, ethylene is by far the more important chemical feedstock since the demand for ethylene feedstocks is about double that for propylene feedstocks. Consequently, there is a definite need for materials and processes for the conversion of relatively inexpensive feedstocks to ethylene. At the present time, ethylene is produced almost exclusively by the dehydrogenation or pyrolysis of ethane and propane, naphtha and, in some instances, gas oils. About 75% of the ethylene is produced at the present time by steam cracking of ethane and propane derived from natural gas, since natural gas contains from about 5 volume percent to about 60 volume percent of hydrocarbons other than methane, with the majority being ethane. However, relatively severe conditions, particularly temperatures in excess of about 1000.degree. C., are required and, as indicated, such processes are highly energy intensive. In order to reduce the severity of the conditions, particularly temperature, numerous proposals to catalyze pyrolytic reactions have been made. While some of these processes do, in fact, reduce the severity of the conditions, the conversion of the feedstock and the selectivity to ethylene are still quite low. Of particular interest in this phase of the art, is the oxidative conversion of methane to higher hydrocarbons, particularly ethylene and ethane and, more particularly, ethylene. However, these processes have, heretofore resulted in low conversions of methane and poor selectivity to ethylene and ethane.
More recently, it has been discovered that certain solid contact materials are highly effective for the oxidative conversion of feed organic compounds to product organic compounds in the presence of a free oxygen-containing gas, particularly, for the oxidative conversion of methane to higher hydrocarbons, and the oxidative dehydrogenation of saturated C.sub.2 through C.sub.7 hydrocarbons to less saturated hydrocarbons. In the discussions of these contact materials, as well as the contact materials of the present invention, references are made to certain components as "base" materials, while other components are referred to as "promoters". However, it is to be understood that such designations are not to be considered as functionalizing designations, since the base materials, as well as the promoters, are all active components of the contact materials and the base materials are not inert bases or carriers for the promoting materials.
Commonly assigned U.S. patent applications Ser. No. 713, 653, Ser. No. 713,656 and Ser. No. 713,674, all filed Mar. 19, 1985, disclose compositions and contact materials for oxidative conversion in which the base materials are Group IIA metal oxides. U.S. application Ser. No. 713,673, filed Mar. 19, 1985, relates to compositions and contact materials for oxidative conversion in which the base material is zinc oxide. U.S. application Ser. No. 742,340, filed Jun. 7, 1985, utilizes a base material comprising titanium oxide. U.S. application Ser. No. 742, 337, filed Jun. 7, 1985, utilizes lanthanum and Lanthanum Series metals as base materials. Each of these base materials may be promoted with at least one Group IA metal and/or a halogen. To the extent that the contact material is prepared without a halogen, or with an inadequate amount of halogen, U.S. application Ser. No. 742,335, filed Jun. 7, 1985, discloses that the lack of halogen may be made up by at least intervally adding a halogen, or a halogen precursor, during the course of the reaction. The entire contents of each of these applications are incorporated herein by reference.